Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1135 AM EDT Mon Jul 02 2018 Valid 12Z Thu Jul 05 2018 - 12Z Mon Jul 09 2018 ...Overview and weather threats/highlights... A closed upper high will settle into the Rockies/Four Corners region by late this week and weekend as upper troughing over Canada dips into New England. This evolution will bring a warming trend to a majority of the West into northern Plains (some readings 10F or more above normal) and cooler temperatures (back near average) to the East. Even with the episode of upper troughing over the eastern U.S., expect above average heights aloft over nearly the entire lower 48. Precipitation will generally focus around the periphery of the upper high. The most agreeable signal for highest 5-day rainfall totals exists near the central Gulf Coast where a retrograding upper level inverted trough/low and possible weak surface reflection may enhance activity. Clouds/rainfall will tend to keep temperatures near to just below average over the Gulf Coast region. A front progressing from the Great Lakes-central Plains into the East/South will bring a period of showers/thunderstorms with some locally heavy rainfall. Another frontal system/upper shortwave progressing through the Northwest into the northern Plains should bring mostly light/scattered precipitation to the Northwest/northern Rockies and then showers/storms to the northern Plains-upper MS Valley. ...Guidance evaluation/preferences... The updated forecast reflected little meaningful change from previous issuance. There is still sufficient agreement for significant features in principle to favor an operational model blend days 3-5 Thu-Sat followed by a model/ensemble mean blend to account for typical increase in forecast uncertainty at extended time frames. Detail issues of note: 00Z/06Z GFS runs become faster and more sheared than most other guidance for the upper feature that retrogrades along the Gulf Coast, with the model blend providing 70 percent weight of the non-GFS scenario. Individual model runs and ensemble spaghetti plots suggest increasing shortwave detail uncertainty (without well-defined clustering among ensemble systems) over the northeastern Pacific/western North America by days 6-7 Sun-Mon. This spread tempers confidence a bit for details of the northern Plains front late in the forecast. Rausch/Fracasso WPC medium range forecasts of 500 mb heights, surface systems, weather grids, quantitative precipitation, and winter weather outlook probabilities are found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4